Debenture is a greek word which means to owe. Debenture & shares are differently used.
Meaning of mortgage
Adebenture is a long-term debt instrument used by governments and large companies to obtain funds. It is similar to a bond except the securitization conditions are different. A debenture is usually unsecured in the sense that there are no liens or pledges on specific assets. It is however, secured by all properties not otherwise pledged. In the case of bankruptcy debenture holders are considered general creditors.